Constant velocity joints (CVJ joints) and other rotational joints are common components in automotive vehicles. Typically, constant velocity joints are used where a transmission of constant velocity rotating motion is required. The common types of constant velocity joints are plunging tripod, a fixed tripod, a plunging ball joint and a fixed ball joint. These types of joints are currently used in front wheel drive vehicles, rear wheel drive vehicles and on propeller shafts found in rear wheel drive, all wheel drive, and four wheel drive vehicles. The constant velocity joints are generally grease lubricated for life and sealed by a sealing boot when used on driveshafts or half shafts. Therefore, constant velocity joints are sealed in order to retain grease inside the joint and keep contaminates, such as dirt and water out of the joint. To achieve this protection the constant velocity joint is usually enclosed at the opened end of an outer race by a sealing boot made of a rubber, thermoplastic, or silicone type material. The opposite end of the outer race generally is enclosed by a dome or cap, known as a grease cap in the case of a disk type joint. A mono block or integral stem and race design style joint is sealed by the internal geometry of the outer race. This sealing and protection of the constant velocity joint is necessary because contamination of the inner chamber of the joint generally will cause damage to the joint.
A main function of the constant velocity joint is the transmission of rotational forces and torque. A plunging joint will transmit rotational velocity while permitting relative axial displacement within the joint. Generally, a tripode joint operates as a plunging constant velocity joint while providing some degree of axial articulation. In typical joint assemblies, a variety of bolted joint designs are used to assemble a joint to a propshaft or halfshaft within the automotive vehicle. These propshaft and halfshaft assemblies are typically assembled prior to installation within a driveline of a vehicle.
When a joint is installed within a vehicle, the lubricant within the joint will tend to exert a force on the boot when the joint is rotating thus causing deformation. Deformation of the boot is undesirable because damage to the boot my result from boot-to-boot contact. Damage to the boot causes loss of lubricant from the joint and contamination of the joint with water and debris. Additionally, lubricant is a very expensive component of a joint. Reducing the volume of lubricant is desirable for cost savings and to minimize the forces exerted on the boot and causing deformation. However, decreasing the volume of lubricant in a joint, with nothing more, may result in a joint with inadequate lubrication of the internal components resulting in a less effective joint. What is needed, therefore, is a system for decreasing the volume of lubricant in a joint while still maintaining adequate lubrication of the internal components.